Learn Hardcore Portuguese (Brazil): É bom caminhar na cidade.

In Portuguese, é bom is commonly used for general statements or opinions that apply broadly. For instance, É bom ir ao médico (It’s good to go to the doctor). Conversely, está bom tends to refer to a more temporary state (“It’s fine/It’s okay right now”). Since the sentence is making a general statement about walking in the city, é bom is the natural choice.

Why "caminhar" instead of "andar" or "passear"? Are they interchangeable?

All three can refer to moving on foot, but caminhar emphasizes the act of walking itself, often for exercise or leisure. Andar is a more general verb meaning “to go” or “to move around on foot,” and passear can imply a more leisurely, perhaps sightseeing-oriented walk. In the sentence É bom caminhar na cidade, the idea is that walking is good, possibly for health or exploration, so caminhar is very fitting. However, using andar or passear would still be understandable, just with a slightly different nuance.

How is "na" formed? Should I say "em a" instead?

The word na is a contraction of em + a. In Portuguese, prepositions and articles often merge when they appear together:
• em + a → na
• em + o → no

So you wouldn’t say em a cidade in normal speech or writing; you would use na cidade to mean “in the city.”

Is "É bom caminhar na cidade" a general statement about any city, or is it specifically talking about one city?